In the construction of roads and paths, the existing soil is frequently used to produce a new base course therefrom, which is particularly suitable for the application of a new surface layer (paved layer). The existing soil is milled and crushed by ground milling machines and in most cases blended with a bonding agent, which can be bulk material (for example, lime, cement or fly ash). A base course is then prepared, for example, by compression of the bound milled material. Such ground milling machines are, in particular, recyclers or stabilizers, so that the following disclosure of the present invention relates more particularly to a recycler or a stabilizer with the described features, although, for the sake of clarity, these two machine types will not be explicitly referred to as preferred embodiments throughout.
Milling of the underlying ground surface and mixing of the bulk material into the milled soil are frequently carried out by means of a self-propelled ground milling machine, which usually includes a drive motor, for example, an internal combustion engine, a machine frame, an operator's platform, traveling means, such as wheels or crawlers, and a milling drum, more particularly, one mounted in a milling drum hood. The milling drum is a substantially hollow cylindrical body, on the external surface of which a number of milling tools are disposed, which, during operation of the ground milling machine, are driven, due to rotation of the milling drum, into the underlying ground surface to mill the same. At the same time, there is carried out crushing of the milled material and mixing of the milled material with the bulk material present on the soil surface. In order to ensure thorough mixing of the bulk material with the milled soil, the bulk material is deposited on the soil to be milled prior to milling by the milling drum, for example, by means of a spreading vehicle traveling ahead thereof.
The variant with a spreading vehicle driving ahead suffers from the economic and ecological drawback that undesirable losses frequently occur due to wind scatter. The first solutions proposed for this problem are disclosed in DE 20 2008 012 104 U1, which describes a work train by means of which a silo truck ahead deposits the bulk material directly in front of the ground milling machine in an area covered, for example, with dust shield mats. Thus, it relates to a work train comprising two self-propelled machines, both of which need a driver. Alternatively, it is known to design the ground milling machine with its own appropriate spreading system, as described in DE 10 2009 008 884 A1. The ground milling machine disclosed in this citation has its own silo or its own storage container, from which the bulk material is poured out in front of the milling drum. Practical experience, however, has shown that the bin capacity of the accompanied silo is too low, so that only comparatively short work periods are possible. Furthermore, it is known to transport bulk material pneumatically, while traveling, from a silo truck ahead to the ground milling machine, so as to increase the bin capacity for bulk material in this way. However, this approach is relatively complicated and, particularly because of the pneumatic conveying system, it is also relatively expensive to operate and maintain.
It is, thus, an object of the present invention to provide a work train for mixing bulk material into the underlying ground surface, by means of which the problems relating to the prior art are avoided and economic and dust-free dumping of bulk material onto the ground surface is made possible.